Method of making composite stock



Dec. 6, 1949 H. w. scHULTz ET AL METHOD 0F MAKING COMPOSIITE STOCK Filed July 7', 1945 BY OLAF RAS/H0530! ATTORNE S Patented a 6, 1949 OFFICE METHOD OF MAKING COMPOSITE s'roox Harold W. Schultz, John M. Robertson, and Olaf Rasmussen, Dayton, Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application July 7. 1945, serial No. 603,599

` s claims.

. l This invention relates to composite stock and -a method for making such stock and is particuthrough the'medium of a porous metal layer and,

wherein said suitable material is sprayed onto the porous metal. This invention is directed to another method for making -said stock wherein the spraying of the suitable material is eliminated. I

In the present invention, it is a primary object thereof to form composite stock wherein a metallic material such as aluminum, babbitt, or other suitable metal is applied to the surface of a porous metal on steel stock through a rolling operation whereby the applied metal is mechanically worked into the pores of the porous vmetal and thereby interlocked to the steel through the medium of the porous metal layer.

It is a further object of the invention to continuously apply metal strip to porous metal on steel strip.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accomf a cross section of the composite stock formed showing the penetration of the rolled metal into the porous metal layer.

Referring particularlyto Fig. 1, one embodi- 'ment of the invention is shown wherein a metal strip 20 is fed simultaneouslywith a porous metal on steel strip 22 to a pair of rolls 2t wherein the vmetal of strip 28 is mechanically worked into the porous metal whereupon'the composite strip 2B preferably passes into anannealing furnace 28,

I wherein the composite strip is annealed for relieving strains therein and for alloying the metal of strip 20 with the porous metal layer when said metals are alloyable. Fig. 2 shows another einbodiment of the invention wherein the strip 20 andthe porous metal on steel strip 22, are fed directly into an annealing furnace 28, which furnace 28 includes pressure rolls 30? therein. In this embodiment, the pressure required for rolling the metal of strip 20 into the porous metal is less than in the embodiment shown in Fig. 1-since the strip 20 is hot and is more ductile and, therefore, ows 'more readily' intol the pores of the porous metal. In both instances the metaliof strip-20 is mechanically worked into the pores of the porous metal. It is desirable that the porous metal layer is formed of a metal strong in co1npression such as, copper-nickel alloy, copper-iron alloy or some other strong metal or alloy thereof since the rolling step tends to deform the porous metal and if a, weak structure is provided, deformation thereof occurs prior to the time that the metal of strip 20 is thoroughly worked into the pores thereof.

The porous metal is applied to the steel by sintering and may be made from non-compacted metal powder as disclosed in Koehring Patents 2,198,253 and 2,198,254, or it may be formed from compressed metal powder which has been sintered with void forming compounds therein whereby the porosity of the layer is at least 40%. In each case, the porous metal layer is metallurgically bonded to the steel support and has a minimum thickness equal to the diameter of one particle of powder used in the porous metal layer. Any metal strip 20 may be used, such as; aluminum, or yalloys thereof, silver, alloys thereof, babbitts, lead, alloys thereof or in fact any metal which can be rolled into the porous metal layer. In this connection, any metal which has greater ductility than the porous metal at the temperature of rolling `can be used.

We have found that pressure rolls 24 and 30 should be so set that the metal of strip 20 is thoroughlyworked into the 'pores of the porous metal Without appreciably deforming the porous metal. Thus, for the bestresults, trial runs should be made with different settings of the pressure rolls after which cross sections of the stock should be examined metallographically. After rolling, the strip is preferably annealed to relieve strains and/ or cause metallic diiusion,if possible, between the juxtaposed layers. The annealing furnace is heated, as is well known in the art, to a temperature suflicient to properly anneal the rolled in metal depending upon the time of annealing. The 4primary factors being that the rolled in 3 metal becomes alloyed with the porous metal at its boundary line and that the strains set up by the rolling step are relieved. In some cases, it may be desirable to melt the rolled in layer, particularly in the case of babbitts. In this instance, side rails may be provided for the strip to prevent the molten metal from being lost. Obviously the temperature of heat treatment must be below the melting point and the dissolution temperature of the porous metal layer.

In the embodiment, shown in Fig. 2, the rolls 30 are positioned at a point within the annealing furnace sufficiently remotefrom the entrance to permit preheating of the strip 20. In this instance, it is desirable that the strip attains a temperature suilicient to soften the strip 20 so as to reduce the pressure necessary for the rolling in operation prior to rolling. Obviously this temperature is not limiting since the rolls may be placed external of the furnace as shownin Fig. 1 but to gain any substantial benefit over the externally placed rolls, the strip should be preheated. Also the preheating will provide a better bond between the metal of the strip 20 and porous metal since the strips in passing through the annealing furnace are uxed to a certain extent by the atmosphere within the furnace which is a non-oxidizing atmosphere and preferably a reducing atmosphere. Obviously a reducing atmosphere will increase the iluxing by removing certain oxides from the surface of the metals.

It has been found that rolled in metal actually flows under rolling either hot or cold and is mechanlcally forced into the pores of the porous metal to completely fill the pores whereby satisfactory interlock is obtained.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a method of making composite stock the steps comprising; providing a highly porous metal layer metallurgically bonded to strong non-porous metal said highly porous metal layer being formed by sintering loose, substantially non-compacted superimposing the more ductile stock upon thel through the medium of the porous metal layer.

metal powder onto the surface of the non-porous metal for forming a layer having pores which inherently include reentrant angles therein, rolling a sheet of a metal of continuous extent and more ductile than the porous metal layer onto the surface of the porous metal whereby portions of the more ductile metal are forced into the pores of the porous metal.

2. The method defined in claim 1 with the said stocks, at a temperature below the melting point of either said stocks and under reducing conditions for nuxing the surfaces of said stocks,

4. In the method of making composite stock, the steps comprising; provided a highly porous metal layer metallurgically bonded to a strong non-porous metal, said highly porous metal layer being formed by sintering loose, substantially non-compacted metal powder onto the surface of the non-porous metal for forming a layer having pores-which inherently include reentrant angles therein, and then rollingA a sheet of lead alloy material of continuous extent and more ductile than the porous metal layer onto the surface ofthe porous metal whereby portions of the lead alloy are forced into the pores of the porous metal.

5. In the method of making composite stock, the steps comprising; providing a highly porous metal layer metallurgically bonded to a strong non-porous metal, said highly porousmetal layer being formed by sintering loose, substantially non-compacted metal powder onto the surface of the non-porous metal for forming a layer having pores'which inherently include reentrant angles therein, and then rolling a sheet of aluminum material of continuous extent and more ductile than the porous metal layer onto the surface of the porous metal whereby portions of the aluminum are forced into the poresof the porous metal.

6. In the method of making composite stock, the steps comprising; providing a highly porous metal layer metallurgically bonded to a strong non-porous metal, said highly porous metal layer being formed by sintering loose,` substantiallyv non-compacted metal powder onto the surface of the non-porous metal for forming a layer having pores which inherently include reentrant angles therein, and then rolling a sheet of aluminum alloy material of continuous extent and more ductile than the porous metal layer onto the surface of the porous metal whereby portions of the aluminum alloy are `forced into the pores of the porous metal.

` HAROLD W. SCHULTZ. JOHN M. ROBERTSON. OLAF RASMUSSEN.

v REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS 

